Pressure converter means



Jan. 2, 1951 E. A. ROCKWELL PRESSURE CONVERTER MEANS 5 Sheets-Sheet 1 Original Filed Jan. 4, 1940 VENTOR .Qmw

ATTORNEY umig Jan. 2, 1951 E. A. ROCKWELL 2,536,140

PRESSURE CONVERTER MEANS Original Filed Jan. 4, 1940 5 Sheets-Sheet 2 A/ Mam/4 ATTORNEY 1951 E. A. ROCKWELL 2,536,140

PRESSURE CONVERTER MEANS Original Filed Jan. 4, 1940 5 Sheets-Sheet 5 1 i 1 miuuum: J 27 Q: E I

g m a: i Y;1z2 Q: 2! 3 9 m 124 v Q E 4 INVENTOR ATTOR: EY

Jan. 2, 1951 E. A. ROCKWELL 2,536,140

PRESSURE CONVERTER MEANS Original Filed Jan. 4, 1940 5 Sheets-Sheet 4 GAL Can ATTORNEY Jan. 2, 1951 E. A-. ROCKWELL 2,536,140

PRESSURE CONVERTER MEANS Original Filed Jan. 4, 1940 5 Sheets-Sheet 5 INVENTOR iw-MAQ w ATTORN E Patented Jan. 2, 1951 UNITED STATES PATENT OFFICE PRESSURE CONVERTER S Edward A. Rockwell, Cleveland, Ohio Application February 17, 1943, Serial No. 476,248, new PatentjNo. 2,410,750, dated November 5, 1946, which is a division of application Serial No. 312,356,,January 4, 1940, now Patent No. 2,331,800, dated October 12, 1943. Divided and this application April 6, 1944, Serial No. 529,868

3 Claims. 1

My invention relates particularly to an appa ratus for controlling the application of power involving pressure converter means for the operation of different parts or accessories of automotive vehicles, as for example automobiles, aeroplanes, railroad cars, mine locomotives, etc.

This application is a division of my copending application Ser. No. 476,248, filed February 17, 1943, upon Controlling System for the Application of Power, now Patent No. 2,410,750, which was a division of my application Ser. No. 312,356, filed January 4, 1940, upon System for Controlling the Application of Power, now Patent No. 2,331,800, granted October 12, 1943.

The object of my invention i to provide converter means which may be used in systemsof the above character. Another object is to provide means for converting one pressure to another, as for instance low pressure to high pressure. My invention is adapted to be applied, not only for the operation of heavy-duty parts, as for instance on heavy trucks, requiring a considerable volume of pressure fluid for the operation of the same but also for the operation of relatively light parts on aeroplanes and other automotive vehicles, such for instance as light trucks, etc. Still another object is to provide an unloader valve. Another object is to provide a converter valve. Further objects of my invention will appear from the detailed description of the same hereinafter.

While my invention is capable of embodiment in many different forms, I have shown only certain embodiments thereof in the accompanying drawings, in which- Fig. 1 is a diagrammatic elevation of a system made in accordance with my invention, adapted for heavy duty, involving the application of a modulated low pressure and so as to apply thereafter a modulated high pressure;

Fig. 2 is a vertical section of an accumulator for pressure adapted to be used therewith;

Fig. 3 is an end elevation of the same;

Fig. 4 is a vertical section through the same on line 4-4 of Fig. 2; I

Fig. 5 is a vertical section of a pressureconverter adapted to be used therewith;

Fig. 6 is an elevation of the same;

Fig. '7 is a plan view of the same;

Fig. 8 is a cross-section of the same taken on line 88 of Fig. 5;

Fig. 9 is a longitudinal section of one of the modulator valves;

Fig. 10 is a vertical section of a convertervalve;

iii

' high pressure thereby.

There is provided therein a reservoir gravityfeed tank I having a filler opening 2, an inlet 3 for the returned discharged liquid, which may be a hydraulic brake fluid or any other suitable liquid, and a removable cylindrical screen filter 4 located over anoutlet or. supply opening 5 which leads .by a pipe-6 to a rotary pump 7 which may, for example, be any, desired type of gear pump. This is driven by an electric motor 8.

Pressure liquid is thus supplied from the pump 1 by a pipe 9 to. an inlet ID on a pressureaccumulater H. The pressure'fiuid from the pump 8 is thus received in a chamber I2 in. a cylinder 13 so as to force to the left inFig. 2, a piston l4 which is mounted by means of a screw [5 one. plunger 16 between which piston l4 and plunger l6 there is a chevron packing ll, of suitable material. .A snap ring stop 18 for the plunger, I6 is located at the. left of the cylinder I3, which latter is screw-threaded, and provided with a pair of ears l9 and 20 secured together with a bolt 2|, for screw-threaded attachment to a spring casing 22. The said plunger l6 rests against the face of a spring retainer plate 23. The spring casing 2'2 also has a split ring stop 24 for the retainer plate 23, which is also provided with an internal sleeve 25 to act as a guide fora plurality of Belleville spring washersZB which are merely dished rings of spring steel. As shown in the drawings, the said rings 2'0 are located so that the adjacent rings have their dished portions extending in opposite directions, said rings being thus carried in an annular chamber. 21 between the casing. 22 and the guide 25 at intervals along the chamber 27. Between groups of the spring washers 23 there are ring-shaped blocks 28 to aid in. maintaining the alignment of. the spring washers 26. The left end of the chamber 21- isclosed by a screw-threaded cap-,29, having a pair of ears30. and 3|, screw-threaded to the spring casing 22 and clamped together by a bolt 32. Bolted to the left face of the cap 29 there is a cylindricalswitch housing 34, which extends inwardly within the washer 26, the same having aremovable screw-plug 35 to permit access to the switch terminals for 1eads36 andv 31 leading to the switch terminals. A cover plate 38 is bolted to the switch housing 34. In said cover plate 38 there is a sleeve 39 having a screw-threaded cap 40 to hold in place a sleeve 4| which has a screw 42 adapted to be received in a slot 43 in the sleeve 39. Said screw 42 also fastens in position an adjustable switch supporting rod 44 provided with a screw-threaded hole 45 to aid in the removal thereof. Slidably mounted on the rod 44 there is a copper plate 46 which operates as a starting switch in the initial starting or setting of the switch apparatus, said plate 43 being normally held in its farthest position to the left by a light spring 41. The other end of said spring 41 abuts against a nut 48 on a sleeve 49 carried on the rod 44, said nut 48 having a washer 59 spacing it from an insulated ring carried on the sleeve 49 and which supports two rod-shaped terminals 52 and 53 connected to said lead 31 and 36 respectively. The copper plate 46 is designed to initially close the circuit manually between the said two rods 52 and 53. The righthand end of the rod 52 and 53 have screw-threaded thereto conducting plates 54 and 55 which are designed, in the automatic operation of the apparatus, to close the circuit with a copper disk 53 carried on a circuit-breaker sleeve 5! slidable within the sleeve 49 and normally held towards the right in Fig. 2 by a spring 58 to close the said circuit. It will be noted that the lead 36 is connected to one terminal 59 at one side of the motor 8 and the other lead 31 leads to any suitable source of electrical energy, as for example a battery, not shown, which latter is also connected by a lead 69 to a terminal 9| on said motor. The right-hand end of the rod 44 has a stop 62 cooperating with the interior of a shell '63 which is formed on the end of the circuit-breaker sleeve 51. This shell 63 is adapted to be moved for the automatic making and breaking of the pumping circuit by a ring 64 mounted on a cylindrical member 55 carrying-within the same a snap action circuit breaking member 66, the inner left portion of which rests against a spring housing 61, having a spring 68 within the same carried on the outside of a sleeve 69 which overlies a rod 10, having a headed screw II and a washer -'I|a supporting near one end thereof a washer I2 held in place by a snap ring 12a to retain said member 55 by springs I1, resting against extensions 79 on arms 79 on which the bell-crank levers I3 and 74 are carried by means of pivots 80.

The arms I9 form a part of the switch housing 34. The rod III, after passing through the snap action member 66, at the right thereof, carries a spring sleeve 8| having therein a spring 82 supported on a sleeve member 83 around the rod III, which latter has a shoulder 34 supporting an end washer 85 to act as a retainer for said spring 82. The

right-hand end of the rod III has a screw-thread '36 which is secured within the spring retainer vplate 23 by means of nuts 81.

Notches 88 in the face of the cylindrical member 65 also cooperate with said rollers 75 and I6 so as to retain the pump circuit broken when the pressure-liquid line is broken, that is to say when the piston I4 is at the extreme right-hand end of the cylinder I3. However, when the said liquid line is complete and the pump motor has been started manually by moving the copper plate 46 to the right, the pump will be started to supply the pressure liquid therefrom to the cylinder I2 and the piston I 4 will move to the left, accordingly, until the snap action circuit-breaker 66 breaks the circuit when the desired pressure has been accumulated, so that, thus, liquid is supplied from the cylinder I2 through a port 89 and thence through radial ports 90 in a valve sleeve 9| which is normally kept in elevated position by means of a spring 92 carried in a cage 93 screw-threaded into the end of the cylinder I3. The lower end of the cage 93 has a slotted opening 94 to permit removal thereof, the same being covered with a screw-threaded apertured dust cap 95. Above the cage 93 there is a screw sleeve 95a, the adjusted position of the sleeve being maintained by a screw 93 cooperating with a series of slots 9'! in said sleeve. This adjustment of the sleeve 95a also permits the tightening of an annular seal 98 located above a washer 99, the seal 98 being supported on the other face thereof by a spacing member M9 which rests against an apertured sleeve Ii I within which the valve member 9| slides. A check valve I92 is carried within the valve member 9| and is held on its seat by a spring I93. The pressure liquid which is thus supplied by the force from the piston I4 is discharged past the check valve I02 and thence to a discharge port I94 leading to a pipe I05, this discharged pressure being a uniform pressure, preferably of about 500 lbs. per square inch.

Another discharge pipe I95 conveys the pressure liquid at this same pressure from the discharge port I94 to a fitting I01 in the upper end of a low-to-high pressure converter I98, Fig. 5, which fitting IIJ'I also acts as a guide for a valve stem I09 of a valve III] which is initially in its open position in the first part of the operation of the automotive accessory to be operated by the pressure liquid. This open position of the valve III] is insured by a shoulder member III held in place by a snap ring IIIa on the lower end of said valve, which shoulder member cooperates with the rear face of a plunger II2 secured by screw II3 to a piston II4 which operates within a cylinder I I5 in the upper part of the low pressure converter I08. A sealing ring H6 is located between the plunger H2 and the piston II4.

Thus, the lower end of the valve H0 is adapted to move within a cylindrical chamber I I I within the piston I I 4, having a communication port I Hat with the cylinder H5, the shoulder member III being normally held in its upper position by a spring II8 to seat the valve H9 and located around a guide-rod II9 screw-threaded within the piston H4 at the lower end thereof. The lower end of said piston I I4 carries a large piston I20 and a sealing ring IZI which operate within an enlarged cylinder I22, the lower end of which is closed by a screw-threaded cap I23 having clamping ears I24 held together with a bolt I 25. Said cylinder has a retracting spring I22a for the pistons H4 and I20. A normally closed air bleeder screw I25 is carried in the lower face of the cap I 2'3 and is removable from the screw I26a having an air escape port I261) to permit the escape of air. At the upper end of the enlarged cylinder I 22 there are a plurality of breather openings I2'I. Each of these openings l2! carries a screw-threaded shell I28 having an air port I29, said shell being secured by a screwthread and cotter-pin I30 to a cover I3I filled with horsehair I32 so as to convey the filtered air therethrough to a tube I33 leading to an inlet port I 34 and the cylinder I22. The pres sure liquid thus passes through the normally -'-'ropen"'-valve II II 'to an ioutlet pipe 'I3'5 and thence to a high'pressure inlet port I flfi -in' a modulator '-valve' :having acasing I 31.

'The -said modulator valve casing 131, "Fig. 9,

h'as se'cured to the -'upperrend thereof, by means "of' a locking screw I38, a "pedal bracket l139 provided with apivot i lil for afoot treadle I I I. The --sai'd--treadle N I has aboss I42- on-th'e lower face *thereof which bears 'upon a plunger M3 dn the pedal bracket-I69 and is-protected from access' of dus't by' a rubber' boot i I M.

Said mo'dulator valve 154, 'Fig. -9, 'is 's'li'dable 'viithin a sleeve I 55 having ports I56 communicat- 'ing' with a low pressure outlet port -I 51 connected by apipe I58 to the reserve-tank I"by mean 'io'f "the-port -3. Am-annularruliberiseal t9iis provided between the sleeve I55 and the sleeve M1.

Another-annular seal |6U'islocated on th'e other side-of the-sleeve I5 5' adjacent'to a -met'alllidspacingmembe IIilgadjacent to which there is -a seal I BIa and'a ported sleeve I62 having a seal I 6 3--communicating with the pressure liquid" port 'I3'6. Adjacent-tosaid seal I 63 there is a ported sleeve 1513 which leads to a modulated pressure :portI'65. It-will be note'dthat the-spacing memb'er IBI has a valve'seat I66-to cooperate-with a conical valve I61 on the cylindrical Valve I5 1. Also on the outside'of said cylindrical valve I54 there is "an annular recess I68 communicating with'ports I69 therein leading to a longitudinal passageway I in the said. valve I54. A strong spring l'll'norm'ally m'oves the cylindrical valve I54 to seat'the valve-I 61 against its seat I66. The disk valve I52 is thus manually movable by the treadle 'I 4I so that-by first keeping the disk'valve "I52closed'ma'nually'on its seat I53 the cylindrical valve' I54 maybe moved downwardly,-in Fig. "9, so as'to open-communication, past the valve I61, between'theport I35 and the interior of said .valve 154 "and 'thence to the modulated pressure port I65.

Thexmodulated pressure thus passes from' th'e port 'I65by-a'pipe -I13to-a'tubular T-block I14 having one branchl leading to the'brake actuation apparatus, and 'whichmaybe comprised of 'two tubular connections I16 and I 11 leading,"re- 'spectively, to "brake operating'devi'ces I18 "and 119. Each of 'thelatter carries 'a piston I-8II,"in 'a-cylin'der 'I8I,'which'isconnected by a rod {I82 tothebrake'shoes inthe usual way,the cylinder .118 or "I19 beingconn'ected with a bracket "I83 fastenedto the "frame'o'f the automobile. Ifdesired, a further tubular connection I'M may branch" rearwardly from the tubular connections .115 and -.I11, for connecting the same with"a:i 5

trailer; for which'purpose there may be a manu- "al shut-off valve I85 having -'a flexible tubular connection I86 leading to a manual shut-off valve 181 which in turn is provided with a tubular connection 'I88'leading to tubular branchesISQ' and "I QITlea'ding,respectively, to brake-operating units "I9 I and I92 constructed like the brake-operating units'I18 and I19. I

When themodulated pressure provided through "the-pipe I13-has moved the brake shoesinto their positionfor 'applying'thereafter the braking force, "the pressure in the pipe I15 "will rise and -"this pressure'takes effect through a-pipe I93 connected 'to the T block l14 which leadsto a port F94 in t a fitting I 95 of Y a converter valve 'ha-ving at the other side thereof a normally closed "air 'bleederW'BQFig. 10. =Within thefitting I95 there isa plunger-I91 having an annular seal- I'98-mov- "able'within a'cylindrical chamber I 99, the-"other fend:df wliich has a screw sleeve 2 00 to actasan '6 ahutmentiforzia sprin'g =2 01 whichrnormallyr'torces itherplunger 1191 ito'ithe might, in LEElig. Jill). :Acrod 2 20111 011 the left send :of ithe :plunger sci-I1 iipass'es zt'hroughitheiscrewasleeveri flflzandbears onmfmd 3 2-02 constructed :the same and having parts rand =valve''conn'ections the same ias ':the \rod 1M5. ZThis ifittin'g 5 I 95 is secured :by screws :22 03 :to :r zvalve c"a;sing 22M gconstructed rexactly (the .tsame :an'd :vprovide'd with thesame ;kind :of valve as ;.in:1the

: zvalve casin'g:=I31 previouslydescribed. ":Intthiszinstance the valve within the casing' izMlis'moved iby th'e pressur'e accumulated-within:the :pipe I 93 iso as'to'akeep theis'aid valve open duringlthieacom itinuance ofisaidipressuresand: thus,tat1that 'Ltime,

e15 to transmit the .pressureIfluidrreceivedifromtthe pipe I05 through said valve and thence through aipip'ezfi'ito aiporti 2 06: inzth'e: cap I2 3 :off thewlowhigh ;pressure converter I 08. tilI he low pressure rliquid discharged from 1.17118 valv'ewasing 7204 "when fithe :high v pressure within @the pipe I193 1ceases,i.is discharged by .a1pipe75201 through mport 208 onthe inlet sidecof :therpump 1,' -which-' is ztalso connected to the pipe. 6. ilnathis way, when the pressures in the pipe 2 Il 51hasrrbeen applied,'ias above :referred to, the :piston .I2II (21S 'movedtupwardly, ithuseclosing :the valve I lo'sand thex-low itpressurefinlet into the :cylinder I508, "the *iconstructiomof thetvalve :I I I Lbein'g zsuch as ito kper'mitfansample flow of liquid past itheisame when :open 1: and so as to :avoidwea'r ton utheiseal '1 for the valve 1 I I I]. Thereafter 1 .theshigh pressure diquid -produced by E'the low :pressure converter I 08 is'supplied' throughv thepipe': I3 S vvhich; isaithen modul'ated fby :the imodulator valve: in theucasing I 31 =-andithus delivered as 'modulatedrhigh .apres- -sure:through 'the pipes I Band I 15 tor-the brakes so *asitotapply this high pressure to secure '5 the zbrakingzelfecttonathe brake shoes.

; In the operation of my invention: as .sh'owniin s4 Fig. 1, when it is desired to-put' onthe brakesxxor eoperate riany other part :of the I automotive vehicle itheipedal I4 I 'is 'moved downwardly and the relaatively "low ezpressure liquid vreceived through the inert I36, due tolthe closure of .the valve I52,"is

145 2allowel1 sto ,pass by the valve I61 in modulated :amounts',thence through the "port I69 and out =17h10llghffthe port I65 to thepipes I1L3 land I15 rand "then :to the brakes to initially "move "the -rbrake2shoes into position. Whenthe pressuredn ethese gpipes accumulates to a higher pressure,

:thisipressure reacts through the pipe I93'on-to -ithe-converter'evalve 294 to keep the said valve :opennwhile this'high pressure condition continues, lthe'result of which is to causexthe 10w pressure liquid'treceived by saLid valveZiM-from thepipe: I05 =-toipass :'by the apipe "2'05 to'the low :pressure for large acylinder end'of the low-to-high pressure 'c'onverter I 08, thereby closing the valve I I II and .Jplacing the "liquid under high pressure in:.the

1 rcylinder :II5, which is :then discharged :Jbyithe *pipezl35lto be modulated by the: modulator valve ;:'.I'31.'. and ithence 'delivered'in'the form of high zpressurezbythelpipes I13 "and I15 tothe brake shoesxfforiproducing athe braking efiect "thereon.

. This "braking pressure can be modulated,'=that isitorsayincreasedior decreased at will, according to the increments or partial release of the'liquid in theipipes I13: and 1 I 15 by 1 the valve I31. Upon 'the releasei ofathe' pedal I 4 I the-partsiare restored 1 -:tofitheir:initialepositions; the iexhaustliquidzpassing by :the 'pipe II58 ':to '"the reservertank zI t-ian'd iffrom "the' valveizll l :by Zthe :pipe 1 201 ito zthel'low pressure' -side of tathe ipump :1. Throughout lathe operation asidescribedfabove,'theiaccumulator '-:I I

7-5 wvlllrmanitalnttlrereinadandy of2liomitlmnderitne minimum desired pressure, which may be approximately 100 lbs. per square inch, ready to be utilized whenever desired upon the actuation of the pedal Ml. By this means a relativeiy low pressure is provided for initially setting the brakes, followed by modulated high pressure for applying the braking force. Also, if desired, the brakes can be operated by the manual force through the continuous body of the hydraulic fluid to the brakes in case of failure of the other liquid pressures.

While I have described my invention above in detail I wish it to be understood that many changes may be made therein without departing from the spirit of the same.

I claim:

1. A low pressure converter comprising a hydraulic line leading to the converter, a conduit leading from the converter for moving a workperforrning device, a relatively low liquid pressure supply constructed and arranged to supply liquid to said line under superatmospheric pressure, a large piston and a smaller piston connected together, cylinders for said pistons each of which a separate inlet, said line having branches leading to said inlets, a pressure responsive valve controlled by the pressure in the conduit, said valve being located in the branch leading to the large cylinder, and a valve having a lost-motion connection to said first mentioned piston and operable thereby, adapted to close said line by the movement of the pistons, said pressure responsive valve being responsive to a predetermined pressure in the conduit to admit fluid from the source to the large cylinder to act on the pistons and thereby close the valve connected to the pistons, said pistons thereafter intensifying the pressure of the liquid in the small cylinder, said pistons being spring pressed towards their withdrawn position.

2. A low pressure converter comprising a hydraulic line leading to the converter, a conduit leading from the converter for moving a workperiorming device, a relatively low liquid pressure supply constructed and arranged to supply liquid in said line under superatmospheric pressure, a large piston and a smaller piston connected together, cylinders for said pistons each of which has a separate inlet, said line having branches leading to said inlets, a pressure responsive valve controlled by the pressure in the conduit, said valve being located in the branch leading to the large cylinder, and a valve having a lost-motion connection to said first mentioned piston and operable thereby, adapted to close said line by the movement of the pistons, said pressure responsive valve being responsive to a predetermined pressure in the conduit to admit fluid from the source to the large cylinder to act on the pistons and thereby close the valve connected to the pistons, said pistons thereafter intensifying the pressure of the liquid in the small cylinder, said pistons being spring pressed towards their withdrawn position and said conduit having a control valve therein for controlling the liquid supplied through said conduit for work-performance.

3. A low pressure converter comprising a hydraulic line leading to the converter, a conduit leading from the converter for moving a work- 'performing device, a relatively low liquid pressure supply constructed and arranged to supply liquid to said line under superatmospheric pressure, a spring-retracted large piston and a smaller piston connected together, cylinders for said pis-- tons each of which has a separate inlet, said line having branches leading to said inlets, a pressure responsive valve controlled by the pressure in the conduit, said valve being located in the branch leading to the large cylinder, the small cylinder having located at its outer end its inlet and a connection to said conduit, and a valve having a lost-motion connection to said first mentioned piston and operable thereby, adapted to close said line by the movement'of the pistons, said pressure responsive valve being responsive to a predetermined pressure in the conduit to admit fluid from the source to the large cylinder to act on the pistons and thereby close the valve connected to the pistons, said pistons thereafter intensifying the pressure of the liquid in the small cylinder.

4. A low pressure converter comprising a hydraulic line leading to the converter, a conduit leading from the converter for moving a workperforming device, a relatively low liquid pressure supply constructed and arranged to supply liquid to said line under superatmospheric pressure, a spring-retracted large piston and a smallor piston connected together, cylinders for said pistons each of which has a separate inlet, said line having branches leading to said inlets, a pressure responsive valve controlled by the pressure in the conduit, said valve being located in the branch leading to the large cylinder, the small cylinder having located at its outer end its inlet and a connection to said conduit, and a valve having a lost-motion connection to said first mentioned piston and operable thereby, adapted to close said line by the movement of the pistons, said pressure responsive valve being responsive to a predetermined pressure in the conduit to admit fluid from the source to the large cylinder to act on the pistons and thereby close the valve connected to the pistons, said pistons thereafter intensifying the pressure of the liquid in the small cylinder and said conduit having a control valve therein for controlling the liquid supplied through said conduit for work-performance.

5. A low pressure converter Comprising a hydraulic line leading to the converter, a conduit leading from the converter for moving a workperformin device, a relatively low liquid pressure supply constructed and arranged to supply liquid to said line under superatmospheric pressure, a large piston and a smaller piston connected together, cylinders for said pistons each of which has a separate inlet, said line having branches leading to said inlets, a pressure responsive valve controlled by the pressure in the conduit, said valve being located in the branch leading to the large cylinder, and a valve having a lost-motion connection to said first mentioned piston and having a valve-seating spring within the small piston having its base seated on the large piston, adapted to close said line by the movement of the pistons, said pressure responsive valve being responsive to a predetermined pressure in the conduit to admit fluid from the source to the large cylinder to act on the pistons and thereby close the valve connected to the pistons, said pistons thereafter intensifying the pressure of the liquid in the small cylinder, said pistons being spring pressed towards their withdrawn position and said valve having a valve seat on the small cylinder.

6. A low pressureconverter comprising a hy draulic line leading to the converter, a conduit leading from the converter for moving a workperforming device,,a relatively low liquid pressure supply constructed and arranged to supply liquid to said line under superatmospheric pressure, a large piston and a smaller piston connected together, cylinders for said pistons each of which has a separate inlet, said line having branches leading to said inlet, a pressure responsive valve controlled by the pressure in the conduit, said valve being located in the branch leading to the large cylinder, and a valve having a lost-motion connection to said first mentioned piston and having a valve-seating spring within the small piston having its base seated on the large piston, adapted to close said line by the movement of the pistons, said pressure responsive valve being responsive to a predetermined pressure in the conduit to admit fluid from the source to the large cylinder to act on the pistons and thereby close the valve connected to the pistons, said pistons thereafter intensifyin the pressure of the liquid in the small cylinder, said smaller piston being spring pressed towards the withdrawn position and said valve having a valve seat to control the inlet on the small cylinder.

7. A low pressure converter comprising a hydraulic line leading to the converter, a conduit leading from the converter for moving a workperforming device, a relatively low liquid pressure supply constructed and arranged to supply liquid to said line under superatmospheric pressure, a, spring-retracted large piston and a smaller piston connected together, cylinders for said pistons each of which has a separate inlet, said line having branches leadin to said inlets, a pressure responsive valve controlled by the pressure in the conduit, said valve being located in the branch leading to the large cylinder, and a valve having a lost-motion connection to said first mentioned piston and operable thereby, adapted to close said line by the movement of the piston, said pressure responsive valve being responsive to a predetermined pressure in the conduit to admit fluid from the source to the large cylinder to act on the pistons and thereby close the valve connected to the pistons, said pistons thereafter intensifying the pressure of the liquid in the small cylinder, the said two cylinders having bores which are made in one piece,

and said valve having a valve seat to control the inlet on the small cylinder.

8.- A low pressure converter comprising a hydraulic line leading to the converter, a conduit leading from the converter for moving a workperforming device, a relatively low liquid pressure supply constructed and arranged to supply liquid to said line under superatmospheric pressure, a spring-retracted large piston and a smaller piston connected together, cylinders for said pistons each of which has a separate inlet, said line having branches leading to said inlets, a pressure responsive valve controlled by the pressure in the conduit, said valve being located in the branch leading to the large cylinder, and a valve having a lost-motion connection to said first mentioned piston and operable thereby, adapted to close said line by the movement of the pistons, said pressure responsive valve being responsive to a predetermined pressure in the conduit to admit fluid from the source to the large cylinder to act on the pistons and thereby close the valve connected to the pistons, said pistons thereafter intensifying the pressure of the liquid in the small cylinder, the said two cylinders having bores which are made in one piece, and said valve having a valve seat to control the inlet on the small cylinder.

EDWARD A. ROCKWELL.

REFERENCES CITED The following references are of record in the file'of this patent:

UNITED STATES PATENTS Number Name Date 1,550,089 Mattingly Aug. 18, 1925 4 1,847,604 Finsen Mar. 1, 1932 1,885,235 Davis Nov. 1, 1932 1,887,880 Avery Nov. 15, 932 1,938,979 Sawtelle Dec. 12, 1933 2,162,797 Boldt June 20, 1939 2,308,712 Peterson Jan. 19, 1943 FOREIGN PATENTS Number Country Date 769,257 France June 5, 1934 

